High efficiency, high power density and high reliability have always been the industry's requirements for power converters. High efficiency means less energy consumption, which helps to save energy, protect environment and reduce operation cost. High power density stands for small size, lightweight and less space requirement, thereby reducing construction cost. High reliability means longer service life and lower maintenance cost.
High efficiency, high power density and high reliability are closely related with excellent thermal management. Firstly, at a lower operating temperature, conduction losses of power devices such as MOSFET and IGBT may be reduced, which is beneficial to improve system efficiency. Secondly, on many occasions heat density directly determines power density. The power converter is a system for processing power conversion. Generally speaking, semiconductor devices generate high heat losses, but tolerable temperatures of the semiconductor devices are limited. And the semiconductor devices may be disabled or deteriorated sharply in performance in case of beyond the tolerable temperatures. Therefore, to control the temperature of a semiconductor chip within an acceptable range, a high-efficiency heat dispassion system is of vital importance. Thirdly, the lifespan of the semiconductor device is closely linked with temperature. Lower operating temperature may prolong the service life of the semiconductor device. An engineering experience exists in the electronic field: the lifespan of the semiconductor device may be shortened by half whenever temperature rises by 10 degrees. It can be known that a good thermal management is of vital importance for improving the conversion efficiency, power density and reliability of the power device.